This invention relates generally to particle separators and detectors which are used in conjunction with lubrication systems for mechanical equipment which utilize a fluid such as oil. In particular, the invention selectively discriminates particles above a predetermined size in the oil of lubrication systems. It also includes a filter contained within the apparatus to selectively retain particles. A self closing valve may be combined with the filter so it may be removed without the requirement that the oil be drained.
Mechanical power transmission equipment is subject to wear due to friction, caused by the contact of moving parts under pressure at high relative speeds. This results in an abrasive wearing of the surface with the resulting release of small particles. Such "wear particles" are generally less than 20 microns in size. Particles of this size are suspended in the oil and generally move with it rather than reacting promptly to gravity and inertial forces. Once such particles are suspended in the oil they act as abrasives, thus reducing the lubrication effect of the oil. Such particles are generally removed from the oil through the use of filters which are introduced into the system, or by magnets which may be used if the particles are of ferrous nature.
When the components of the power transmitting system which is being lubricated become overloaded or when localized areas of weakness occur, particles of material become loosened, generally at the point of contact between moving parts under high surface pressure. Once the surface has been deformed by the breaking off of such particles the rate of deterioration is accelerated resulting in the breaking off of additional particles at an increasing rate. These "failure particles" are generally of a much greater order of magnitude in size than the previously referred to "wear particles". Additionally, the quantities of wear particles produced are substantially increased. Failure particles generally fall into the 100 to 2000 micron size range. Due to their greater mass they are less subject to being suspended in the lubricating fluid.
It is well known that the structural failure of drive train components may be predicted in advance of such failure by monitoring the condition of the lubricating oil. Such structural failure is indicated when metallic particles in the size range of failure particles are detected, i.e. greater than 100 microns, or when the quantity of wear particles substantially increases. The present invention is of the type that detects failure particles.
The prior art is replete with descriptions of various apparatus which will detect the presence of failure particles. Some of these apparatus use filters of varying mesh size which are periodically checked so as to determine the presence of wear particles. This approach is not appropriate for aircraft applications as it does not lend itself to in-flight monitoring. Other apparatus use electronic devices wherein wear particles are detected by the disturbance of a magnetic or electric field by wear particles. A problem associated with such apparatus has been that an accumulation of wear particles may produce the same signal as a failure particle thus resulting in a false indication. Additionally, such magnetic detectors are highly dependent upon the sensor which is used in determining the overall accuracy and sufficiency of the apparatus. U.S. Pat. Nos. 2,936,890 issued May 17, 1960 and 3,432,750 issued Mar. 11, 1969 to Botstiber are examples of magnetic chip detectors. U.S. Pat. No. 3,317,042 issued May 2, 1967 to Botstiber is an example of an apparatus which combines a filter with a circuit completion type sensor.
As previously indicated, most lubricating systems contain filters for removing particles. Of course, such filters require periodic replacement. Various mechanisms are disclosed in the prior art for replacing such filters without requiring that the lubricating fluid in the system be drained.
The various apparatus and structure required for detecting wear particles, filtering the lubrication fluid, and enabling filters to be changed without draining the system increase the weight and complexity of such systems. This weight and complexity is particularly undesirable and detrimental for aircraft applications.